Tuneable NFC-enabled device

Abstract

An NFC-enabled device configured at least in part as an integrated circuit, the integrated circuit including a controller and a plurality of capacitors. The controller is operable to control one or more of the plurality of capacitors to vary an operating parameter of the NFC-enabled device.

What is claimed is: 
     
       1. A near field communications (NFC)-enabled device, comprising:
 a magnetic field sensor configured to sense a magnetic field strength to provide a sensed field strength signal; and 
 a controller configured to vary an operating parameter of the NFC-enabled device in response to the sensed field strength signal using a peak detection process, the controller being further configured to:
 change the operating parameter in a plurality of increments until a final increment adversely affects the operating parameter; and 
 set the operating parameter to an increment immediately before the final increment; 
 
 wherein the magnetic field sensor is further configured to generate the sensed field strength signal to cause the controller to vary the operating parameter when the magnetic field strength is less than a threshold. 
 
     
     
       2. The NFC-enabled device of  claim 1 , further comprising:
 a plurality of capacitors, coupled to the controller, at least one of the plurality of capacitors being configurable to be activated or deactivated by the controller to vary the operating parameter. 
 
     
     
       3. The NFC-enabled device of  claim 2 , further comprising:
 a plurality of switches, each switch from among the plurality of switches being associated with at least one capacitor from among the plurality of capacitors, 
 wherein the controller is configured to control at least one of the plurality of switches to activate or deactivate its associated at least one capacitor to vary the operating parameter. 
 
     
     
       4. The NFC-enabled device of  claim 2 , wherein the at least one capacitor comprises:
 first and second conductive track portions provided in a common layer of the NFC -enabled device, the first and second conductive track portions being spaced from one another to form, respectively, first and second electrodes of a first capacitor. 
 
     
     
       5. The NFC-enabled device of  claim 4 , wherein the first and second electrodes each include a plurality of transversely extending spaced conducting tabs, the first and second electrodes being arranged such that the plurality of transversely extending spaced conducting tabs of the first electrode are interleaved with the plurality of transversely extending spaced conducting tabs of the second electrode. 
     
     
       6. The NFC-enabled device of  claim 4 , further comprising:
 third and fourth conductive track portions provided in a second common layer of the NFC-enabled device that is different from the common layer and which is spaced therefrom by an insulating layer, the third and fourth conductive track portions being spaced from one another to form, respectively, first and second electrodes of a second capacitor from among the plurality of capacitors. 
 
     
     
       7. The NFC-enabled device of  claim 6 , wherein the first electrode of the first capacitor is coupled to the first electrode of the second capacitor, and the second electrode of the first capacitor is coupled to the second electrode of the second capacitor, the first and the second capacitors being arranged one above the other such that laterally extending tabs of the first capacitor overlie laterally extending tabs of the second capacitor. 
     
     
       8. The NFC-enabled device of  claim 2 , wherein the plurality of capacitors comprises:
 a fixed capacitor; and 
 a plurality of switchable capacitors in parallel with the fixed capacitor. 
 
     
     
       9. The NFC-enabled device of  claim 1 , wherein the operating parameter comprises at least one of:
 an induced voltage; and 
 an induced current. 
 
     
     
       10. The NFC-enabled device of  claim 1 , wherein the controller is configured to implement the peak detection process using a proportional, integral, differential (PID) processing algorithm, the PID processing algorithm being represented by: 
       
         
           
             
               
                 
                   PE 
                   ⁡ 
                   
                     ( 
                     t 
                     ) 
                   
                 
                 + 
                 
                   
                     1 
                     I 
                   
                   ⁢ 
                   
                     
                       ∫ 
                       
                           
                       
                       
                           
                       
                     
                     ⁢ 
                     
                       
                         E 
                         ⁡ 
                         
                           ( 
                           t 
                           ) 
                         
                       
                       ⁢ 
                       
                         ⅆ 
                         
                           ( 
                           t 
                           ) 
                         
                       
                     
                   
                 
                 + 
                 
                   D 
                   ⁢ 
                   
                     ⅆ 
                     
                       ⅆ 
                       t 
                     
                   
                   ⁢ 
                   
                     E 
                     ⁡ 
                     
                       ( 
                       t 
                       ) 
                     
                   
                 
               
               , 
             
           
         
       
       wherein t is a time, E is the sensed field strength signal, P is a proportional error, I is an integral of an error, and D is a derivative of the error. 
     
     
       11. The NFC-enabled device of  claim 1 , further comprising:
 an inductive coupler; 
 wherein the controller is further configured to vary the operating parameter of the NFC-enabled device to vary a resonant frequency of the inductive coupler. 
 
     
     
       12. A method of operating a near field communications (NFC) -enabled device, comprising:
 generating a magnetic field strength signal from a detected magnetic field near the NFC-enabled device when the magnetic field strength signal is less than a threshold; 
 adjusting a capacitance of a plurality of capacitors by a first increment to vary an operating parameter of the NFC-enabled device upon receipt of the magnetic field strength signal; 
 adjusting the capacitance of the plurality of capacitors by a second increment to vary the operating parameter; and 
 determining whether the second increment adversely affects the operating parameter when compared to the first increment. 
 
     
     
       13. The method of  claim 12 , further comprising:
 adjusting the capacitance by the first increment when the second increment adversely affects the operating parameter. 
 
     
     
       14. The method of  claim 12 , further comprising:
 adjusting the capacitance of the plurality of capacitors by a third increment to vary the operating parameter when the second increment does poi adversely affect the operating parameter. 
 
     
     
       15. The method of  claim 12 , wherein the determining comprises:
 determining a first and a second magnetic field strength in response to the first and second increments, respectively; and 
 comparing the first magnetic field strength and the second magnetic field strength to determine whether the second increment adversely affects the operating parameter. 
 
     
     
       16. The method of  claim 12 , wherein the adjusting the capacitance by the first increment comprises:
 adjusting the capacitance by the first increment to vary a resonant frequency of an inductive coupler. 
 
     
     
       17. A near field communications (NFC)-enabled device, comprising:
 an inductive coupler configured to inductively receive a signal; 
 a magnetic field sensor configured to sense a magnetic field strength of the signal; 
 a controller configured to vary an operating parameter of the NFC-enabled device in response to the magnetic field strength using a peak detection process, the controller being further configured to:
 change the operating parameter in a plurality of increments until a final increment adversely affects the operating parameter; and 
 set the operating parameter to an increment immediately before the final increment; 
 
 wherein the magnetic field sensor is further configured to generate a sensed field strength signal from the sensed magnetic field strength to cause the controller to vary the operating parameter when the magnetic field strength is less than a threshold. 
 
     
     
       18. The NFC-enabled device of  claim 17 , further comprising:
 a plurality of capacitors, coupled to the controller, at least one of the plurality of capacitors being configurable to be activated or deactivated by the controller to vary the operating parameter. 
 
     
     
       19. The NFC-enabled device of  claim 18 , further comprising:
 a plurality of switches, each switch from among the plurality of switches being associated with at least one capacitor from among the plurality of capacitors, 
 wherein the controller is configured to control at least one of the plurality of switches to activate or deactivate its associated at least one capacitor to vary the operating parameter. 
 
     
     
       20. The NFC-enabled device of  claim 18  wherein the plurality of capacitors comprises:
 a fixed capacitor; and 
 a plurality of switchable capacitors in parallel with the fixed capacitor. 
 
     
     
       21. The NFC-enabled device of  claim 17 , wherein the controller is further configured to vary the operating parameter of the NFC-enabled device to vary a resonant frequency of the inductive coupler.